Auto PEP8

Ran autopep8 against codebase. Not tested.
https://pypi.python.org/pypi/autopep8
More pep8 cleanup

Some hands on cleaning. Mostly refactoring comments and string constants
Format code to PEP8, #18. Fixed tests in Python 2.6 and added unittest2 as a test requirement for Python <= 2.6. Fixed a bug in Path.add() where in some cases the absoluteness of the Path wasn't preserved.